黄淮海地区夏玉米干旱等级划分

干旱是影响黄淮海地区夏玉米产量稳定性的主要农业气象灾害。建立夏玉米干旱灾害指标，开展夏玉米干旱灾害的监测及评估，对农业防灾减灾意义重大。该文根据夏玉米生长发育过程，选择土壤相对湿度和作物水分亏缺指数分别建立夏玉米不同生育阶段的干旱等级指标。首先在综合分析有关夏玉米土壤水分指标研究成果的基础上，确定了夏玉米各生育阶段不同干旱等级的土壤相对湿度指标。在此基础上，利用河南省农业气象观测站多年观测资料，建立水分亏缺指数与土壤相对湿度之间的关系模型，利用已确定的土壤相对湿度指标计算得出夏玉米不同生育阶段不同干旱等级的水分亏缺指数干旱指标。根据土壤相对湿度指标，夏玉米播种-出苗、出苗-拔节、拔节-抽雄、抽雄-乳熟和乳熟-成熟5个生育阶段发生轻旱的临界值分别为65%、60%、70%、75%和70%，发生重旱的临界值分别为45%、40%、50%、55%和50%，发生特旱的临界值分别为40%、35%、45%、50%和45%；而根据水分亏缺指数指标，5个生育阶段发生轻旱的水分亏缺指数的临界值分别为35%、40%、20%、10%和35%，发生重旱水分亏缺指数临界值分别为50%、65%、55%、45%和65%，发生特旱的临界值分别为55%、75%、65%、55%和75%。在黄淮海夏玉米区选择代表站点对确定的干旱等级指标进行了验证，土壤相对湿度和水分亏缺指数判定的干旱等级相同及相差一个等级的百分率变化在71%～91%，表明2套指标对干旱发生情况的判别具有较好的一致性；通过与历史典型干旱年份灾情对比，2套指标能够较好的判定出历史年份夏玉米生长季干旱发生情况，能够用于夏玉米干旱的监测、评估等方面的科研及业务服务中。

Drought grade classification of summer maize in Huang-Huai-Hai area

Abstract: Drought is the main agrometeorological disaster of summer maize production in the Huang-Huai-Hai area in China. Establishing the drought grade indexes for more effective monitoring and evaluation is of great significance to the prevention and mitigation of agricultural disasters. There have been lots of published research results about the effects of different soil water conditions on growth, development, yield components and yield of summer maize. However, there are large differences about stage division and grade classification among different researches, and it is difficult to apply and compare in different regions. In this paper, soil relative moisture and crop water deficit index were selected to establish the drought grade indexes according to the growth process of summer maize. The whole growth duration of summer maize was divided into five stages, namely sowing to emergence, emergence to jointing, jointing to tasselling, tasselling to milking and milking to maturity. Drought was classified into five grades, including no drought, light drought, moderate drought, strong drought and severe drought. The drought grade indexes were determined for each stage and grade. The used data included crop phenology, soil water and daily weather record. By analysis and summary of the published results, a set of drought grade indexes based on soil relative moisture were determined. And this set of index included each stage of summer maize from sowing to maturity. The established index was convenient for application because its consistency among stages and grades. After the determination of grade indexes of soil relative moisture, the relationship models between soil relative moisture and crop water deficit index were set up using the observing data at 16 agrometeorological stations in Henan Province. Then, the grade indexes of crop water deficit index were calculated using the relationship models on the basis of the determined soil relative moisture indexes. According to the index of soil relative moisture, the critical index value at five stages of summer maize was 65%, 60%, 70%, 75% and 70% for light drought, respectively; it was 45%, 40%, 50%, 55% and 50% for strong drought and 40%, 35%, 45%,50% and 45% for severe drought, respectively. According to the index of crop water deficit index, the critical index value at five stages of summer maize was 35%, 40%, 20%, 10% and 35% for light drought, respectively; it was 50%, 65%, 55%, 45% and 65% for strong drought and 55%, 75%, 65%, 55% and 75% for severe drought, respectively. The two established drought grade indexes were validated in the Huang-Huai-Hai area by selecting typical stations. Validated results showed that the two indexes are well consistent with the consistency of 71%-91% for the identification of drought grades. Meanwhile, the identification results by the two indexes were basically consistent with the historical occurrences of drought disasters. Therefore, the drought grade indexes established in this paper could be used in the future monitoring and evaluation of drought in summer maize production in the Huang-Huai-Hai area.